1. Field of Invention
The present invention relates to a sliding material having improved sliding properties under a mixed lubricating condition and a boundary lubricating condition. More particularly, the present invention relates to a sintered sliding material, which consists of metal backing, a Cu or Cu-alloy layer sintered on the metal backing, and resin and solid lubricant which are filled in the pores formed in the sintered layer around the particles of the Cu or Cu-alloy.
2. Description of Related Arts
It is known from Japanese Unexamined Patent Publication No. 55-106,230 that 30% by weight or less of polyimide and such lubricating additives as molybdenum disulfide and graphite can be filled in the pores of a sponge metal, e.g., Cu, having porosity of from 88 to 98%. The sponge metal having a very large porosity is the substrate material which supports the filled materials. As is described in said publication, the blanking of the sponge metal is usually necessary for shaping it into the form of a bearing. The recovery of the workpieces by the blanking is, however, disadvantageously low. In addition, the formability of the sponge metal is poorer than that of the sliding material which comprises the metal backing.
Japanese Examined Patent Publication No. 63-37445 discloses a sintered sliding material of the type described above. That is, a Cu or Cu-alloy layer is sintered on the metal backing, and resin and solid lubricant are filled in the pores of the sintered layer. The surface of the sliding material is machined to expose the sintered metal and the filled material. The surfaces of the sintered metal and the filled material therefore form an essentially identical plane.
According to the method for producing the sliding material described in Japanese Examined Patent Publication No. 63-37445, an almost spheroidal lead-bronze powder, having a diameter of 0.18 mm, is sintered on the metal backing and then machined to provide a thickness of 0.11 mm. The thus machined sintered metal is exposed on the surface of the sliding metal at 40-60% of such surface. It is also disclosed in Japanese Examined Patent Publication No. 63-37445 that such solid lubricants as molybdenum disulfide and graphite are desirably limited to an amount of 30% by weight or less. In this case, the amount of the polyimide and polyamide-imide, having a high bonding strength, increases relative to the solid lubricant, and, thus, the effects of the solid lubricant are not outstanding.
Other drawbacks of the known sliding material are described with reference to FIG. 4.